> For the complete documentation index, see [llms.txt](https://maksimdan.gitbook.io/interview-practice-problems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://maksimdan.gitbook.io/interview-practice-problems/leetcode_sessions/349_intersection_of_two_arrays.md).

# 349 Intersection of Two Arrays

Given two arrays, write a function to compute their intersection.

```
Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].
```

Note:\
Each element in the result must be unique.\
The result can be in any order.

**The Idea:** The intersection of two arrays are the elements they have in common.

**Complexity:** O(N) time and space

```cpp
vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
    unordered_set<int> s(nums2.begin(), nums2.end());

    vector<int> intersect;

    for (auto i : nums1) {
        if (s.find(i) != s.end()) {
            s.erase(i);
            intersect.push_back(i);
        }
    }

    return intersect;
}
```

**Python**

```python
class Solution:
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        if not nums1 or not nums2:
            return []
        return list(set(nums1) & set(nums2))
```